Thermionic vacuum tube



May 12, 1925.

W. SCHOTTKY THERMIONIC VACUUM TUBE Filed Aug. 27, 1919 IAIN! k Patented May 12, 1925.

.WALTER S CHOT'IKY, ,OF IBERLIN-O EARLOTTENZB'O'RG, GEREANY, ASSIGNOR. TO

SIEMENS & HALSKE, .AK'IIENGESELLSCHAFT, GERMANY, A CORPORATION OF GERMANY.

'rnnnmomo vacuum was.

Application filed August 27, 1919. Serial no. seam...

eumn man an rnovrsrons or TEE sczr or IABGH a, 1921, 41 ans. rag-@1313.

To all whom it may ooncem:

Be it known that I, WALTER SOHO'I'IKY, a German citizen,'residing at Berlin-Charlottenburg, Germany, have invented cer-' 5 tain new and useful Improvements in Thermionic Vacuum Tubes (for-which I have filed applications as' follows: Germany,

May 31,1916, Pat. No. 300,617; France, June 24, 1919, Pat. No. 518,623; Holland, May 28, 1919, Ser. No. 12,100, and Holland, October 1 25, 1920, Ser. No. 16,916; Italy, June 27, 1919, Pat. No. 176,732/52-510; Sweden, June 27, 1919, Ser. No. 2962/19, and Sweden, December 23, 1919, er. No.

1 5,808/19; Switzerland, June 16, 1919,'Pat.

No. 86,781; Norway, December 24, 1919, Ser. No. 18,769; Denmark, April 14, 1920, Ser. No. 994/20; Austria, Ma 15, 1917, Ser. No. A. 2,263-17 Hungary, 'ay 1.91, 1917 Ser. No. S. 8,618; Czechoslovakia, March trode and its particular object is to ima As is well knpwn, the amplification of electrical energy in cathode relays or amplifying tubes provided with a g ow cathode and an auxiliary electrode depends to a considerable degree .-upon the fact, that the controlled current is influenced to a far greater extent by changes in the .potential of the auxiliary or grid electrode or by magnetic influence upon the path of the rays than by changes in the potential of the anode. According to this theory the increase of energy will grow, provided that suitable translators and other parts be employed, at the same ratio as the sensibility of the control current decreases in relation to the variation of the anode potential.

This phenomenon may be interpreted as a kind of reaction of the secondary circuit on what takes place within the amplifying tube. The more this reaction is diminis e the 'greater'will be the amplifying effect.

According to my invention this reaction prove the efliciency of such tubes or relays.-

may be diminished by arranging in" front of the anode an open-worker grid shaped conductor insulated from the anode as well as from the controlling grid electrode, and

possessing a constant voltage relatively to the" cathode. In the following I shall call this conductor a"protective net.

The peculiar action of this protective net is explained by the fact, that it protects OF SIEMBNSSTADT,.NEAR 31 131213},-

electrostatically the field in the vicinity of the auxiliary or grid electrode against the field of the anode, while at the same-time the field-directed from the grid towards "the protective net and partly transgressing into.

the space between cathode and grid causes a considerable part of the electrons to pass through the grid even in the case where, as is recommendable also for other reasons, the grid is given a of the cathode.

potential lower than that In order to provide a ainst a substantron currents,:lower than the potential of the anode. Where space charging effects need not be feared, I even prefer keeping the potential lower than that which would be obtained with the anode voltage used,

but without employing a protective net, at

the point where this net 1s disposed.

In the drawings aflixed to this specification and forming part thereof two different modifications of a tube according to my invention are illustrated, Fig. 1 being an elevation and Fig. 2 a diagram showingthe connections of the first modification, while Fig. 3 is an elevation, Fig. 4 a plan of the electrode arrangement and Fig. 5 a diagram showing the connections of the second modification.

Referrin to the drawings, the electrodes shown in Fig. 1 to be disposed within a xed on a frame '1' formed of glass tubes,

this'frame being fixed in turn to the base 't. The vertical arms of the frame consist of tubes of a larger diameter. Within the frame there is fixed the anode a, con-' sisting of a thin hard metal plate. A thin tungsten wire an is wound around the transverse arms of the glass: frames r in a vertical direction, thus surrounding the anode a on both sides at a certain distance and fully insulated from it. A second layer of wire h, this layer also being insulated, is arranged over the first one in the form of another tungsten wire wound around the longitudinal arms of the frame 1' in a horizontal direction.

The frame further carries detents b and 0 serving as supports for two V-shaped tungsten wires k, 10,, these wires representing the glow cathode of the tube. As shown in Fig. 2 both cathode wires are connected in parallel and thus form a reserve in case one of the wires should burn out. Moreover under ordinary conditions they serve to increase the ctticiencz of the amplifying tube.

The wire grid serving as auxiliary or grid electrode is kept in the usual manner on a slightly negative potential relatively to the cathodewires k k,, and serves for controlling the currents passing from the cathode is to the anode a. On the other hard 7 I the protective net an is connected only at one endto such a point of the battery B, which renders its otential lower than the potential due to t e voltage dror;1 between the cathode and the point where t e grid is located ,as a result of the current flow between theanodc and the cathode.

An especially favourable effect of the amplifying tubes is obtained, if besides the I'OtGCtIVE net another so called voltage net 18 used, this net being arranged in tubes operated with pure electron currents between cathode and grid electrode in order to suppress the space charging efiect of the electrons, and being provided with "a higher positive potential than is due to its surroundings.

A tube of this latter kind is shown in Figs. 3 to 5. The glow cathode is has the form of a single thread, concentrically surrounded by the voltage net 8p, which is enclosed in its turn within the rid electrode it having the form of a cylin rical net, this electrode serving as a controlling device.

The grid electrode is surrounded b the protective net an and this latter is one osed in the anode 0., consisting of a thin iece of sheet metal easily freed of gases. he nets are preferably made of a metal of high melting point, such as iron or nickel, and. the

parts are fixed so that the anode is carried by a las rod d fixed to the base t, the individua nets being fixed thereon by glass beads g, connected therewith by fusing. A similar lass bead carries the metal rod 1 having fixed to its upper end the cathode thread k.

The voltage net 87" and the protective net an are pre erably conductively connected with cac i other and have such a potential relatively to the adjacent electrodes, and are arranged-at such a distance therefrom, that the conditions mentioned above regardin the relation of the potentials of the two a ditional nets to their surroundings are observed I claim:

1. In a vacuum tube of the character described in combination, a glow cathode and a grid electrode both connected to the input circuit, an anode connected to the out ut circuit, and a grid-shaped conductor isposed between said first-named grid electrode and said anode, the potential of said conductor relatively to said cathode being constant and sitive but lower than the potential of said anode.

2. In a vacuum tube of the character described in combination, a glow cathode, an anode, a grid electrode and two grid-shaped conductors disposed between said cathode and said anode and insulated therefrom, one of said conductors having a potential relativel to the cathode lower than that of said ano e, while the other conductor has a positive potential relatively to said cathode exceeding the potential corresponding to its position in the space between the cathode and anode. 1

In testimony whereof I afiix my signature.

WALTER SCHOTTKY. 

